Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$58.58	11.279%	$65.1872	$65.19	$65.20	$65.20
Purchase #2	$94.25	6.492%	$100.3687	$100.37	$100.35	$100.40
Purchase #3	$21.67	13.434%	$24.5811	$24.58	$24.60	$24.60
Purchase #4	$147.53	11.178%	$164.0209	$164.02	$164.00	$164.00
Purchase #5	$181.79	9.650%	$199.3327	$199.33	$199.35	$199.30
Purchase #6	$188.69	8.245%	$204.2475	$204.25	$204.25	$204.20
Purchase #7	$190.33	3.307%	$196.6242	$196.62	$196.60	$196.60
7 purchase totals =	$882.84		$954.3623	$954.36	$954.35	$954.30